Here is source code of the Program to create an Activity to create a Toast in an Application. The program is successfully compiled and run on a Windows system using Eclipse Ide. The program output is also shown below.

Main Activity


package com.example.calculator;

import android.R.color;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

TextView disp, res;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
disp = (TextView) findViewById(R.id.textView1);
res = (TextView) findViewById(R.id.textView2);
Button add = (Button) findViewById(R.id.add);
Button mul = (Button) findViewById(R.id.mul);
Button divide = (Button) findViewById(R.id.divide);
Button sub = (Button) findViewById(R.id.sub);
Button log = (Button) findViewById(R.id.log);
Button clear = (Button) findViewById(R.id.clear);
Button calc = (Button) findViewById(R.id.calculate);
Button change = (Button) findViewById(R.id.color);

add.setOnClickListener(this);
mul.setOnClickListener(this);
divide.setOnClickListener(this);
sub.setOnClickListener(this);
log.setOnClickListener(this);
clear.setOnClickListener(this);
calc.setOnClickListener(this);
change.setOnClickListener(this);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
float result = 0, num1, num2;
Toast var;
switch (v.getId()) {
case R.id.add:
String str =(String) disp.getText();
num1 = Integer.parseInt(str);
disp.setText("");
var = Toast.makeText(MainActivity.this, "Enter other number",
Toast.LENGTH_SHORT);
var.show();
str=(String) disp.getText();
num2 = Integer.parseInt(str);
result = num1 + num2;
break;

case R.id.sub:
num1 = Integer.parseInt((String) disp.getText());
disp.setText("");
var = Toast.makeText(MainActivity.this, "Enter other number",
Toast.LENGTH_SHORT);
var.show();
num2 = Integer.parseInt((String) disp.getText());
result = num1 - num2;
break;
case R.id.mul:
num1 = Integer.parseInt((String) disp.getText());
disp.setText("");
var = Toast.makeText(MainActivity.this, "Enter other number",
Toast.LENGTH_SHORT);
var.show();
num2 = Integer.parseInt((String) disp.getText());
result = num1 * num2;
break;
case R.id.divide:
num1 = Integer.parseInt((String) disp.getText());
disp.setText("");
var = Toast.makeText(MainActivity.this, "Enter other number",
Toast.LENGTH_SHORT);
var.show();
num2 = Integer.parseInt((String) disp.getText());
result = num1 / num2;
break;
case R.id.log:
num1 = Integer.parseInt((String) disp.getText());
result = (float) Math.log(num1);
break;
case R.id.clear:
disp.setText("");
res.setText("");
break;
case R.id.color:
int rand = (int) ((Math.random() * 10) % 3);
Button b1 = (Button) findViewById(R.id.add);
Button b2 = (Button) findViewById(R.id.mul);
Button b3 = (Button) findViewById(R.id.divide);
Button b4 = (Button) findViewById(R.id.sub);
Button b5 = (Button) findViewById(R.id.log);
Button b6 = (Button) findViewById(R.id.clear);
Button b7 = (Button) findViewById(R.id.calculate);
Button b8 = (Button) findViewById(R.id.color);

rand =2;
switch (rand) {
case 0:
b1.setTextColor(color.holo_blue_bright);
b2.setTextColor(color.holo_blue_bright);
b3.setTextColor(color.holo_blue_bright);
b4.setTextColor(color.holo_blue_bright);
b5.setTextColor(color.holo_blue_bright);
b6.setTextColor(color.holo_blue_bright);
b7.setTextColor(color.holo_blue_bright);
b8.setTextColor(color.holo_blue_bright);
break;
case 1:
b1.setTextColor(color.holo_green_dark);
b2.setTextColor(color.holo_green_dark);
b3.setTextColor(color.holo_green_dark);
b4.setTextColor(color.holo_green_dark);
b5.setTextColor(color.holo_green_dark);
b6.setTextColor(color.holo_green_dark);
b7.setTextColor(color.holo_green_dark);
b8.setTextColor(color.holo_green_dark);
break;
case 2:
b1.setTextColor(color.holo_red_dark);
b2.setTextColor(color.holo_red_dark);
b3.setTextColor(color.holo_red_dark);
b4.setTextColor(color.holo_red_dark);
b5.setTextColor(color.holo_red_dark);
b6.setTextColor(color.holo_red_dark);
b7.setTextColor(color.holo_red_dark);
b8.setTextColor(color.holo_red_dark);
break;

default:
b1.setTextColor(color.black);
b2.setTextColor(color.black);
b3.setTextColor(color.black);
b4.setTextColor(color.black);
b5.setTextColor(color.black);
b6.setTextColor(color.black);
b7.setTextColor(color.black);
b8.setTextColor(color.black);
break;
}

break;
case R.id.calculate:
res.setText(Float.toString(result));
break;
}
}

}

Xml

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnCount="2"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<EditText
android:id="@+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="0"
android:textSize="30sp" />

<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="TextView"
android:textSize="30sp" />

<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="40dp"
android:layout_weight="0.29" >

<Button
android:id="@+id/add"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:text="+"
android:textSize="20dp" >
</Button>

<Button
android:id="@+id/sub"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button1"
android:layout_alignBottom="@+id/button1"
android:layout_centerHorizontal="true"
android:text="-" />

<Button
android:id="@+id/mul"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button2"
android:layout_alignBottom="@+id/button2"
android:layout_alignParentRight="true"
android:text="X" />

<Button
android:id="@+id/calculate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_marginBottom="64dp"
android:textAlignment="center"
android:text="Calculate" />

<Button
android:id="@+id/color"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:text="ChangeColor"
android:textAlignment="center"/>

<Button
android:id="@+id/divide"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/add"
android:layout_marginTop="47dp"
android:text="/" />

<Button
android:id="@+id/log"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/divide"
android:layout_alignBottom="@+id/divide"
android:layout_alignLeft="@+id/sub"
android:text="log" />

<Button
android:id="@+id/clear"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/log"
android:layout_alignBottom="@+id/log"
android:layout_alignParentRight="true"
android:text="C" />

</RelativeLayout>

</TableLayout>